<!DOCTYPE html>
<html>
<head>
<title>View transitions: Resizing viewport skips the transition</title>
<link rel="help" href="https://drafts.csswg.org/css-view-transitions-1/">
<link rel="author" href="mailto:bokan@chromium.org">

<script src="/common/rendering-utils.js"></script>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="/resources/testdriver.js"></script>
<script src="/resources/testdriver-vendor.js"></script>

<script>
function waitForAtLeastOneFrame(win) {
  return new Promise(resolve => {
    win.requestAnimationFrame(() => {
      win.requestAnimationFrame(() => {
        resolve();
      });
    });
  });
}

let popupWin;
promise_test(async t => {
  assert_implements(document.startViewTransition, "Missing document.startViewTransition");

  return new Promise(async (resolve, reject) => {
    await waitForAtLeastOneFrame(window);

    // Open a popup window that we'll use to start a transition
    await test_driver.bless('Open a popup in a new window', () => {
        popupWin = window.open('about:blank', 'popup', 'width=300,height=300');
    });
    let popupDoc = popupWin.document;
    popupDoc.documentElement.innerHTML = `
      <style>
        html {background-color: red;}
        html.new {background-color: limegreen;}

        /* Set a no-op animation to show the old snapshot indefinitely. */
        html::view-transition-group(*) {animation-duration: 10s;}
        html::view-transition-new(*) {animation: unset;opacity: 0;}
        html::view-transition-old(*) {animation-duration: 10s;opacity: 1;}
      </style>`;

    // Start a transition inside the popup.
    let transition = popupDoc.startViewTransition(() => {
      popupDoc.documentElement.classList.add('new');
    });

    let finishResolved = false;
    transition.finished.then(() => {
      finishResolved = true;
    });

    // Wait for the transition to start animating.
    await transition.ready;
    await waitForAtLeastOneFrame(popupWin);
    await waitForAtLeastOneFrame(popupWin);

    // Resize the popup window.
    popupWin.resizeTo(popupWin.innerWidth/2, popupWin.innerHeight/2);

    await waitForAtLeastOneFrame(popupWin);

    // `finish` should have resolved as resizing the transition after capture
    // should cause it to skip.
    assert_true(finishResolved, "Transition must be finished by the window resize");
    resolve();
  });
});
</script>
</head>
</html>
